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// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/10/Square/SquareGame.jack
// (same as projects/09/Square/SquareGame.jack)
/**
* Implements the Square Dance game.
* This simple game allows the user to move a black square around
* the screen, and change the square's size during the movement.
* When the game starts, a square of 30 by 30 pixels is shown at the
* top-left corner of the screen. The user controls the square as follows.
* The 4 arrow keys are used to move the square up, down, left, and right.
* The 'z' and 'x' keys are used, respectively, to decrement and increment
* the square's size. The 'q' key is used to quit the game.
*/
class SquareGame {
field Square square; // the square of this game
field int direction; // the square's current direction:
// 0=none, 1=up, 2=down, 3=left, 4=right
/** Constructs a new Square Game. */
constructor SquareGame new() {
// Creates a 30 by 30 pixels square and positions it at the top-left
// of the screen.
let square = Square.new(0, 0, 30);
let direction = 0; // initial state is no movement
return this;
}
/** Disposes this game. */
method void dispose() {
do square.dispose();
do Memory.deAlloc(this);
return;
}
/** Moves the square in the current direction. */
method void moveSquare() {
if (direction = 1) { do square.moveUp(); }
if (direction = 2) { do square.moveDown(); }
if (direction = 3) { do square.moveLeft(); }
if (direction = 4) { do square.moveRight(); }
do Sys.wait(5); // delays the next movement
return;
}
/** Runs the game: handles the user's inputs and moves the square accordingly */
method void run() {
var char key; // the key currently pressed by the user
var boolean exit;
let exit = false;
while (~exit) {
// waits for a key to be pressed
while (key = 0) {
let key = Keyboard.keyPressed();
do moveSquare();
}
if (key = 81) { let exit = true; } // q key
if (key = 90) { do square.decSize(); } // z key
if (key = 88) { do square.incSize(); } // x key
if (key = 131) { let direction = 1; } // up arrow
if (key = 133) { let direction = 2; } // down arrow
if (key = 130) { let direction = 3; } // left arrow
if (key = 132) { let direction = 4; } // right arrow
// waits for the key to be released
while (~(key = 0)) {
let key = Keyboard.keyPressed();
do moveSquare();
}
} // while
return;
}
}
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